Waterproofing generally refers to a process whereby a composition is applied to a wall such as a basement wall to create a water impervious coating thereon. These compositions typically include asphalts dissolved in an organic solvent solution. Applying such compositions generally includes spraying the composition through a conventional air gun or the like and allowing the solvent to evaporate and form the water impervious coating. It is also common to apply a protective board over such coating, the board serving to protect the coating, and/or act as thermal insulation, and/or facilitate the drainage of water away from the walls. These boards typically include foamed polystyrene and fiberglass batts.
The water impervious coating should have good strength and elasticity, as well as demonstrate excellent water resistant characteristics. While these qualities have traditionally been achieved using asphalt based compositions, it has been found particularly useful to employ a polymer based composition, especially one comprising a blend of polymeric materials. This, however, requires compatibility of the polymeric materials so as to prevent separation of phases or ingredients, such separation typically resulting in the degradation of elasticity, toughness, and tack of the elastomeric coating. For purposes of this disclosure, the coatings resulting from polymeric compositions will be referred to as elastomeric coatings.
Employing a composition that is based on a combination of polymeric materials requires a proper physicochemical interaction between the polymer blend and the solvent system employed. Specifically, the solvent system must dissolve the various polymers, as well as impart numerous characteristics to the composition and coating as will be hereinafter recognized.
Of paramount importance, the solvent system must provide a sprayable solution. This typically includes the ability to provide a waterproofing composition having a viscosity less than about 5000 cps at temperatures greater than about 105.degree. F. (40.degree. C.), which is the temperature above which such compositions are commonly sprayed.
It is also very desirous that the solvent system impart a long shelf life to the waterproofing composition. Among the various commercial advantages of a long shelf life are the ability to store and transport the waterproofing compositions over longer periods of time. Shelf life, as will be referred to herein, represents the length of time required for the waterproofing composition will separate or destabilize. In other words, shelf life represents the duration in which the solvent system can maintain proper physicocliemical interaction with the polymer blend. A short shelf life is deleterious because a separated or destabilized composition is often rendered useless and must be reprocessed.
Also of paramount importance, the solvent must provide the ability to apply a uniform and consistent coating on the wall. In fact, architectural specifications require such consistency and uniformity in the coating thickness on commercial and industrial walls, as well as some residential foundation walls. Generally, such specifications only allow a tolerance of +/-20% of the nominal thickness; that is, only a deviation of +/-20% of the desired thickness is permitted. It is believed that thickness uniformity is a function of the solvent system used, as the composition's ability to fill or web-out voids within the surface of the wall depends on the solvent used. Also, it is believed that the solvent employed dictates the consistency of the spray which affects the thickness of the composition, thereby affecting the thickness of the elastomeric coating. It is further believed that the solvent system employed affects the thickness uniformity because the solvent system dictates the drying rate of the composition, as well as the viscosity of the composition as the composition dries.
Not only does the solvent system affect the thickness uniformity of the elastomeric coating, but it is also believed to affect the ultimate quality of the elastomeric coating. For example, improper drying of the composition may cause the composition to skin over, resulting in blisters. Such blisters are believed to occur from the wet composition being too thick in a certain areas, typically resulting from the composition running and sagging on the wall prior to curing. These blisters cause inconsistency in the thickness of the coating and may ultimately provide a weak area where the elastomeric coating may rupture.
A solvent system for a polymer-based waterproofing composition is taught by Roberts et al. in U.S. Pat. No. 5,352,531. Roberts discloses a hydrocarbon resin and block copolymer dissolved in an organic solvent solution, the solvent containing a mixture of toluene and an aliphatic petroleum distillate. The distillate has a boiling range of about 190.degree. F.-230.degree. F., a flash point of about 18.degree.F., a specific gravity of between about 0.709 to about 0.732 and an evaporation rate of about 2.2-2.6. The use of n-heptane or n-hexane is explicitly proscribed. This solution is sprayed to the exterior surface of a concrete foundation and the solvent is thereafter evaporated.
The sprayable composition of Roberts '531, however, exhibits several undesirable characteristics believed to result from the solvent system employed. Particularly, the composition does not spray or dry consistently, which is evidenced by unacceptable inconsistencies in the thickness of the wet composition upon the wall and the final coating. Also, the composition tends to run-down and sag, has a slow drying rate, poor shelf life, and creates inefficiencies such as excessive material waste due to composition run-down prior to cure. Finally, it is believed that the resulting elastomeric coating of Roberts '531 is inferior due to the solvent system employed. This inferiority is generally evidenced by the appearance of the dried coating, as well as the frequency of the blisters that occur.
Thus a need exists to develop an improved solvent solution capable of dissolving a polymer based waterproofing composition for the purpose of spraying the composition onto a wall such as a basement wall. Furthermore, a need exists to develop an improved method of applying such a waterproofing composition to a wall, thereby producing an improved elastomeric coating on the side of the wall to which the composition is applied.